I'm still using the pegs from the 70's or 80s. The springs, rollers and ramp within the freewheel are the consumables - springs are def the first to go, and I've found that there are 'springs' and there are springs ... some seem to collapse a little too easily.
I used to put my clutch assembly together (starter chain removed, obviously) and fit it over the crank taper complete, with key in place.
With an assembly with springs in good condition I now leave the sprocket on the crank (again, chain removed) and fit the freewheel over it while turning the sprocket slowly anti-clockwise to engage it. If the rollers kep falling out your springs are not strong enough. You have to ensure the rollers remain in place and the sprocket can be spun backwards once the freewheel has mated with the taper. If it's a new freewheel you MUST ensure there is a few mm of lateral sideplay for the sprocket between the righthand main and freewheel. Disaster awaits if the gap s too small!!
And I assemble mine completely dry.